1. Field of the Invention
This invention relates to an ultrasonic flaw detecting device for determining abnormalities within a pipe or similar structure. Nondestructive ultrasonic testing of objects such as pipes is well known. With such testing an ultrasonic beam of energy is sent into an object by a transducer and detection of reflections or echoes off internal structure within the object permits determination of characteristics of that internal structure.
More particularly, if a piezoelectric crystal is pulsed with an electrical energy signal, that electric pulse causes an ultrasonic signal to be emitted. It is also known that if the ultrasonic signal reflects off an object within its path and returns to the piezoelectric crystal, that crystal responds by producing an electric signal. It is possible, therefore, to send ultrasonic signals into a test object whose internal structure is of interest and to develop information from crystal output signals which result from the reflections off the internal structure of the object.
2. Prior Art
Ultrasonic techniques for examining the internal structure of a pipe or other cylindrical objects are known. When the object of interest is a pipe and the area of interest within the pipe is a longitudinally extending weld area, it has been more effective in studying the internal structure of the pipe weld area to send the ultrasonic signals into the pipe transverse to the weld area rather than along its length.
One example of a proposed mechanism for determining the internal structure of a pipe or cylindrical object is the U.S. Pat. No. 3,924,453 to Clark et al. The angles of incidence of the ultrasonic beams into the pipe in the Clark device are unequal. If this technique of ultrasonic flaw detection is utilized, the correlation of flaw severity to reflected signal strength becomes difficult due to the non-monotonic variations in the strength of the received echo as a function of distance.
U.S. Pat. No. 3,693,415 to Whittington proposes another form of ultrasonic flaw detection for use with a cylindrical object. The Whittington patent teaches the use of an array of ultrasonic transducers which must be positioned about the pipe in a circular or cylindrical arrangement. Means must be provided for sequentially pulsing the transducers which make up this array in order that ultrasonic beams of the proper phase arrive at a given point in the pipe structure and then enter that structure to be reflected by flaws or irregularities within the pipe.
U.S. Pat. No. 3,916,675 to Perdijon proposes still another method for ultrasonically testing the internal structure of a cylindrical device. The Perdijon device, utilizes a complex deflector means which receives parallel ultrasonic beams from an ultrasound transducer and reflects these beams into the pipe structure. As can be seen by the complexity of the Perdijon proposal much care must be taken in designing the deflector means in order that the angle of incidence of the deflected beam strikes the pipe in the proper angle. The complex design required for the proper reflector shape must be repeated for pipes of different sizes and shapes and the complexity is significantly increased if any variation in detection capability is to be achieved.